[ONOS-6901] Fix how the systemTest does not return any result when it forced to quit the test

Change-Id: If93c48d46e8dc2494046b42de21f732775d7f520
diff --git a/TestON/tests/dependencies/Cluster.py b/TestON/tests/dependencies/Cluster.py
index 6b18b8b..36811ba 100644
--- a/TestON/tests/dependencies/Cluster.py
+++ b/TestON/tests/dependencies/Cluster.py
@@ -405,8 +405,7 @@
                              getattr( ctrl, drivers[ specificDriver ] ) ), function )
             except AttributeError:
                 main.log.error( "Function " + function + " not found. Exiting the Test." )
-                main.cleanup()
-                main.exit()
+                main.cleanAndExit()
 
             t = main.Thread( target=f,
                              name=function + "-" + ctrl.name,